Accounts Receivable - Trade Receivable Balances (Detail) - USD ($) $ in Millions		Mar. 31, 2019	Dec. 31, 2018
Accounts Notes And Loans Receivable [Line Items]
Contract receivables	[1]	$ 838	$ 794
Retainages	[2]	156	155
Accounts receivable—trade, net		977	932
Contract receivables [Member]
Accounts Notes And Loans Receivable [Line Items]
Less allowances		(17)	(17)
Accounts receivable—trade, net		$ 977	$ 932

[1] Unbilled receivables for our performance obligations recognized at a point in time are recorded within Accounts receivable-trade, net and were approximately $44 million and $31 million as of March 31, 2019 and December 31, 2018, respectively.

[2] Retainages classified within Accounts receivable-trade, net are amounts anticipated to be collected within one year and as to which we have an unconditional right to collect from the customer, subject only to the passage of time. Retainages anticipated to be collected beyond one year are classified as Accounts receivable long-term retainages on our Balance Sheet.